1. Field of the Invention
The present invention relates to a camera, in particular to the photographic film holding structure of a camera.
2. Description of Related Art
A device has been disclosed, such as that shown in FIG. 12, which comprises a cross-sectional view showing the photographic film holding structure of a related art embodiment.
As shown in FIG. 12, a pressure plate unit 12 is attached to the back cover 14 of a camera by means of a spring unit 13 provided with springs such as a plate spring. In order for the photographic film 3 to be moved smoothly, the dimensions of the space between the pressure plate surface 12a of the pressure plate unit 12 and the surface of the inner rail 11f facing the pressure plate unit 12, i.e. the inner rail surface 11b, are defined by a space U, which is established so as to be slightly wider than the thickness of the film 3.
The pressure plate unit 12 presses, by the force of the spring unit 13, the film 3 from the back cover 14 toward the inside rail surface 11b. By this means, the film 3 is kept flat in a position facing the aperture A in the camera body 11 that is used for film exposure.
However, in the related art structure shown in FIG. 12, it is necessary that the spring unit 13 press the pressure plate unit 12 from the cover 14 side toward the outer rail surface 11a of the outer rail 11e facing the pressure plate unit 12. A space L2 from the photographic film 3 to the back cover 14 is necessary to accommodate the spring unit 13, thereby requiring the camera to be made larger.
In that structure, thermal deformation in the direction perpendicular to the optical axis of the lens 17 of the camera body 11 and to the direction of feeding of the film 3 is a problem. Even if the outer rails 11e of the camera body 11 deform in the perpendicular direction, the pressure plate unit 12 only makes direct contact with outer rail surfaces 11a due to spring force of the spring unit 13, as was the case before the deformation. Thus, the deformation of the outer rails 11e has no effect upon the pressure plate unit 12. Therefore, even after the deformation of the outer rails 11e, the pressure plate unit 12 does not distort and the film 3 maintains the flatness required for taking a picture.
In order to solve the problem of the large camera size required for spring unit 13 and other problems, applicants have developed the idea of directly anchoring a film regulation component 22 to the camera body 21 as shown in FIG. 5, thereby reducing the space from the photographic film 3 to the back cover 24. In FIG. 5, the regulation component 22 is directly attached to the camera body 21 by mounting screws 26, a space U being provided to enable the smooth movement of the film 3. The position of the film 3 in the direction of the optical axis of the lens 17 is regulated between the film regulation surface 22a of the regulation component 22 and the inside rail surface 21b, thereby keeping the film 3 flat in a position facing the aperture A. When a structure to anchor the film regulation component 22 directly onto the camera body 21 is adopted in this manner, a conventional back cover (one capable of opening and closing from the back of the camera body) becomes unnecessary. The actual mounting of the film is accomplished in such a manner as disclosed in Japanese Laid-Open Patent Application No. 62-156641. The camera disclosed in that publication is structured in such a way that the film rotates around the axis of the cartridge spool of the film, and the front edge of the film is inserted into the film scrolling opening toward the film exposure section from the cartridge chamber. A back cover capable of opening and closing is not present in that camera. Instead, a cover is provided at the bottom of the camera body.
However, when the distance X' from an axis T perpendicular to the optical axis of the lens 17 to the film regulation component mounting surface 21c and the distance Y' from the axis T perpendicular to the optical axis of the lens 17 to the outer rail surface 21a do not match due to variations in the structure within dimension allowances (tolerances), when the regulation surface 22a is tight against the outer rail surface 21a, the regulation component 22 and the camera body 21 warp. As a result, the regulation surface 22a tilts and warps with respect to a preset image-forming surface of the lens 17, thereby making it impossible to maintain the flatness of the film 3 desired for photography, making extra adjustments necessary such as a washer between the regulation component mounting surface 21c and the camera body mounting surface 22b. As a result, the number of production processes has to be increased.
Additionally, heat deformation due to temperature changes in the camera may take place, for example, if a camera is taken out of a car to take a picture in the middle of the summer. Due to temperature changes, heat deformation (thermal expansion) occurs in the camera body 21 and the regulation component 22 in a direction perpendicular to the optical axis 17 and the scrolling direction of the film 3. When the amount of thermal expansion of the camera body 21 and the regulation component 22 differs, the regulation component 22 distorts, resulting in the failure to maintain the desired flatness for the film 3 to take a picture. This problem is caused by the fact that the camera body 21 and the regulation component 22 are each anchored with mounting surfaces 21c and 22b making direct contact with each other.